1. Field of the Invention
The present invention relates to a sheet material positioning method and apparatus, in which sheet materials having a plurality of sizes are conveyed in a predetermined conveying direction so as to be loaded onto a surface plate, and the sheet materials are positioned at a predetermined position on the surface plate.
2. Description of the Related Art
A technique has been developed, in which a printing plate (hereinafter a photopolymer plate) in which a photosensitive layer (e.g., a photopolymer layer) is provided on a support is used, and in which an image is directly recorded on the photopolymer layer of the photopolymer plate by laser beams or the like. (This technique is used in an automatic exposure apparatus for printing plates.)
In this technique, an image is rapidly recorded onto a photopolymer plate, and thus, photopolymer plates need to be sequentially sent. Accordingly, it is preferable that a plurality of photopolymer plates are stacked in advance at a predetermined position and ready to be used, and that the photopolymer plates are automatically taken out one by one so as to be sent into an exposure section. After being sent into the exposure section, the photopolymer plates are preferably conveyed along a predetermined proper conveying path.
The photopolymer plate needs to be wound onto a printing drum at the time of printing, and in order to position the photopolymer plate on the printing drum, an automatic exposure apparatus for printing plates includes a process for forming a punch-hole in the photopolymer plate. The punching is carried out on a surface plate, which serves as a base for the exposure of the photopolymer plate, and is also for the sub-scanning movement. And the punch-hole serves as reference at the time of exposure.
Accordingly, the photopolymer plate delivered onto the surface plate must be positioned at a proper position.
In order to carry out the positioning, initially, an incline of the photopolymer plate is corrected, parallelism of the punch-hole of the photopolymer plate for a center line is corrected. Then, a direction of the photopolymer plate, in which the punch-hole is orthogonal to the center line, is determined based on inversion of output signals from a plurality of sensors (inversion from a photopolymer plate detected state to a photopolymer plate undetected state, or inversion from the undetected state to the detected state), which sensors are provided at positions, which are the corners of the photopolymer plate when the photopolymer plate is at the proper position. Namely, the incline of the photopolymer plate with respect to the center line of the surface plate on the surface plate is corrected, and the position of the photopolymer plate on the surface plate in a direction which is orthogonal to the center line is corrected by using the sensors.
However, the side of the photopolymer plate, which side is in the direction orthogonal to the center line, may have various sizes which are within a range from 400 mm to 745 mm in millimeter interval. Thus, if sensors are provided so as to be at the best position for the each of respective sizes of the photopolymer plates, an enormous number of sensors are required. Therefore, a predetermined number of sensors are disposed at predetermined positions within the above-described range (the predetermined number is a number which is fewer than the number of sizes of the photopolymer plates). The positioning of the photopolymer plate is carried out on the basis of a calculation result from detection results by the sensor. If the sensors are disposed at random positions in this way, the amount of movement for initially detecting a corner of the photopolymer plate by the sensor and the amount of movement obtained by the computations for positioning the photopolymer plate at the appropriate position vary depending upon the size of the photopolymer plate. As a result, there are disadvantages that, for example, the operation efficiency deteriorates, and the positioning accuracy varies depending upon the size of the photopolymer plate.
In consideration of the above facts, it is an object of the present invention to obtain a sheet material positioning method and apparatus, in which, positioning is carried out by a small number of sensors and at the time of positioning the sheet material, amount of movement for positioning can be minimized, and in which, improvement of the operation and stabilization of the positioning accuracy can be archived.
A first aspect of the present invention is a sheet material positioning method, in which, sheet materials having a plurality of sizes are conveyed in a predetermined conveying direction so as to be loaded onto a surface plate, and an incline and a position of the sheet material in a conveying direction of the sheet material with respect to a proper position are corrected, and the sheet material, whose incline and position with respect to the proper position have been corrected, is positioned at a predetermined position on the surface plate by being moved in a direction orthogonal to the conveying direction, by using a plurality of sensors for detecting at least one corner of the sheet material; and wherein at least one dimension of the sheet material in the direction orthogonal to the conveying direction has been recognized in advance; and wherein a sensor, which requires the smallest amount of movement of the sheet material for positioning the sheet material at the predetermined position, is selected from the plurality of sensors based on the recognized dimension of the sheet material, and the corner of the sheet material is detected by the selected sensor.
According to the first aspect of the present invention, with respect to the proper position, after the incline has been eliminated and the positioning in the conveying direction of the sheet material has been corrected, the sensor, which requires the smallest amount of movement of the sheet material for positioning, is selected based on the dimension of the sheet material. As a result, the time for positioning the sheet material can be shortened.
A second aspect of the present invention according to the first aspect is a sheet material positioning method, wherein, after the sheet material has been loaded onto the surface plate, a pressing member, which has a portion that is parallel to a side of the sheet material which side is orthogonal to the conveying direction, presses the sheet material to the proper position, so that the incline and the position in the conveying direction of the sheet material are corrected simultaneously.
According to the second aspect of the present invention, with respect to the proper position, the incline is eliminated and the positioning in the conveying direction of the sheet material is corrected in the following manner: After the sheet material has been loaded onto the surface plate, a pressing member, which has a line connecting at least two points, which line is parallel to a side of the sheet material which side is orthogonal to the conveying direction, is moved to the predetermined position, so that the incline and the positioning in the conveying direction of the sheet material are corrected simultaneously. In this way, the position of the side of the sheet material pressed by the pressing member is fixed, and thus, the sheet material can be easily positioned in the conveying direction thereof. However, since positioning of the sheet material in the direction which is orthogonal to the conveying direction on the basis of a center reference, if the size of the sheet material varies, the position of the sheet material in the direction which is orthogonal to the conveying direction respectively varies. As a result, the positioning method described in the first aspect is required, and the smaller the amount of movement of the sheet material for positioning, the shorter the time for positioning.
A third aspect of the present invention according to the first or second aspect is a sheet material positioning method, wherein the dimension of the sheet material in the direction orthogonal to the conveying direction has different values, the different values are on the basis of a predetermined dimension of 10 mm or lower.
According to the third aspect of the present invention, the sheet material has a number of different sizes, and thus, it is almost impossible in a structural view to dispose sensors optimal for detecting the respective corners of the sheet materials for each of the sizes. Therefore, for example, the smallest and the largest sheet materials are selected, and the sensors are disposed so as to be most suitable only for the selected sheet materials. When the sheet material is of another size, after the corner thereof has been detected by one of the disposed sensors, the difference can be computed so that the sheet material is conveyed.
A fourth aspect of the present invention is a sheet material positioning apparatus, in which, sheet materials having a plurality of sizes are conveyed in a predetermined conveying direction so as to be loaded onto a surface plate, and the sheet material is positioned at a predetermined position on the surface plate, the apparatus comprising: a correcting device, which corrects an incline and a position in the conveying direction of the sheet material with respect to a proper position; a plurality of sensors, which detect at least one corner of the sheet material by movement of the sheet material in a direction orthogonal to the conveying direction; a storing device, which stores at least one dimension of the sheet material in the direction orthogonal to the conveying direction in advance; a selecting device, which, based on the dimension stored in the storing device, selects a sensor from the plurality of sensors, that requires the smallest amount of movement of the sheet material for positioning the sheet material at the predetermined position; and a movement controlling device, which moves the sheet material in the direction orthogonal to the conveying direction based on the sensor selected by the selecting device, and which stops the movement of the sheet material in the direction orthogonal to the conveying direction when the sensor has detected the corner of the sheet material.
According to the fourth aspect of the present invention, initially, the incline and the position in the conveying direction of the sheet material with respect to the proper position are corrected by the correcting device. Next, the sensor, that requires the smallest amount of movement of the sheet material for positioning it at the predetermined position, is selected from the plurality of sensors by the selecting device based on the dimension stored in the storing device. After that, by the movement controlling device, the sheet material is moved in the direction orthogonal to the conveying direction using the sensor selected by the selecting device, and the movement of the sheet material in the direction orthogonal to the conveying direction is stopped when the sensor has detected the corner of the sheet material.
In other words, since the size (dimension) of the conveyed sheet material has been stored in the storing device in advance, which of the plurality of sensors is most suitable can be reliably determined. When the sensor is selected based on the determination, the sensor, that requires the smallest amount of movement of the sheet material for positioning, is reliably selected.
A fifth aspect of the present invention according to the fourth aspect is a sheet material positioning apparatus, wherein, the correcting device is formed of a pressing member, which has a portion that is parallel to a side of the sheet material which side is orthogonal to the conveying direction, and wherein, after the sheet material has been loaded onto the surface plate, the pressing member presses the sheet material to the proper position, so that the incline and the position in the conveying direction of the sheet material are corrected simultaneously.
According to the fifth aspect of the present invention, with respect to the proper position, the incline has been eliminated and the position in the conveying direction of the sheet material is corrected in the following manner: After the sheet material has been loaded onto the surface plate, a pressing member, which has a line connecting at least two points, which line is parallel to a side of the sheet material which side is orthogonal to the conveying direction, is moved to the predetermined position, so that the incline and the position in the conveying direction of the sheet material are corrected simultaneously. In this way, the position of the side of the sheet material pressed by the pressing member is fixed, and thus, the position in the conveying direction of the sheet material can be easily positioned.
A sixth aspect of the present invention according to the fourth or fifth aspect is a sheet material positioning apparatus, wherein the dimension of the sheet material in the direction orthogonal to the conveying direction has different values, the different values are on the basis of a predetermined dimension of 10 mm or lower.
According to the sixth aspect of the present invention, the sheet material has a number of different sizes, and thus, it is almost impossible in a structural view that the sensors are arranged so as to be most suitable for detecting the respective corners of the sheet materials. Therefore, for example, the smallest and the largest sheet materials are selected, and the sensors are disposed so as to be most suitable only for the selected sheet materials. When the sheet material is of another size, after the corner thereof has been detected by one of the disposed sensors, the difference can be computed so that the sheet material is conveyed.
A seventh aspect of the present invention according to any one of the fourth to sixth aspects is a sheet material positioning apparatus, wherein the plurality of sensors include two sensors, which are disposed at positions corresponding to dimensions of smallest and largest sheet materials in the direction orthogonal to the conveying direction.
According to the seventh aspect of the present invention, when at least two sensors, which correspond to the smallest and the largest sheet materials, are disposed, the sheet material can be positioned by being moved by an amount which is smaller than the difference between the smallest and the largest sheet materials (smaller than a distance on the basis of the difference between the smallest and the largest sheet materials).
An eighth aspect of the present invention according to any one of the fourth to sixth aspects is a sheet material positioning apparatus, wherein the plurality of sensors include three sensors, two sensors of which are disposed at positions corresponding to dimensions of smallest and largest sheet materials in the direction orthogonal to the conveying direction, and one sensor other than the two sensors is disposed at a position in substantially middle of the two sensors.
According to the eighth aspect of the present invention, in addition to the seventh aspect, the sensor is added so as to correspond to a medium-sized sheet material whose size is between that of the smallest and the largest ones. As a result, the amount of movement for positioning can be reduced, and further, for example, if the sensor at the middle position is made movable, the sensor can be disposed in accordance with the size of the sheet material which is frequently used by the applied user.
A ninth aspect of the present invention according to any one of the fourth to sixth aspects is a sheet material positioning apparatus, wherein the plurality of sensors include CCD line sensors.
According to the ninth aspect of the present invention, when the CCD line sensors are disposed at predetermined positions, the position of the sheet material can be accurately recognized. Further, the plurality of sensors may be closely arranged so as to form a group of sensors.
A tenth aspect of the present invention according to any one of the fourth to ninth aspects is a sheet material positioning apparatus, wherein the sheet material is a printing plate in which a photosensitive layer is provided on a support.
According to the tenth aspect of the present invention, the printing plate in which the photosensitive layer is provided on the support is used as the sheet material. The printing plate is photosensitive, and thus, it needs to be positioned in a darkroom. Accordingly, automatic positioning by the sensors is necessary. In this case, the positioning apparatus described in the fourth to ninth aspects is effective.
An eleventh aspect of the present invention according to the tenth aspect is a sheet material positioning apparatus, wherein, in a state in which the printing plate is positioned at the predetermined position, a punch-hole for positioning the printing plate at a mounting position on a printing drum is formed in the printing plate.
According to the eleventh aspect of the present invention, in order to form the punch-hole in the printing plate for positioning the printing plate at the mounting position on the printing drum, the positioning needs to be accurately carried out. If the punch-hole is dislocated, color blurring or the like is caused, and as a result, the image quality is deteriorates. Accordingly, the invention described in the tenth aspect, in which both positioning rapidity and positioning accuracy can be archived, is effective.
A twelfth aspect of the present invention is a sheet material positioning method, in which, a sheet material is conveyed in a predetermined conveying direction so as to be loaded onto a surface plate, and the sheet material loaded onto the surface plate is moved in a direction orthogonal to the conveying direction, such that the sheet material is positioned at a predetermined position on the surface plate by a plurality of sensors for detecting the sheet material; and wherein at least one dimension of the sheet material in the direction orthogonal to the conveying direction is recognized; and wherein a sensor, which requires the smallest amount of movement of the sheet material for positioning the sheet material at the predetermined position, is selected from the plurality of sensors based on the recognized dimension of the sheet material, and the sheet material is detected by the selected sensor.
A thirteenth aspect of the present invention according to the twelfth aspect is a sheet material positioning method, wherein, before the sheet material loaded onto the surface plate is moved in the direction orthogonal to the conveying direction, the orientation and position of the sheet material are corrected so that the sheet material has a predetermined orientation with respect to the conveying direction and the sheet material is positioned at a predetermined position in the conveying direction.
A fourteenth aspect of the present invention according to the twelfth aspect is a sheet material positioning method, wherein the corner of the sheet material is detected by the selected sensor.
A fifteenth aspect of the present invention is a sheet material positioning apparatus, in which, a sheet material is conveyed in a predetermined conveying direction so as to be loaded onto a surface plate, and the sheet material loaded onto the surface plate is moved in a direction orthogonal to the conveying direction, such that the sheet material is positioned at a predetermined position on the surface plate by a plurality of sensors for detecting the sheet material, the apparatus comprising: a recognizing portion, which recognizes at least one dimension of the sheet material in the direction orthogonal to the conveying direction; and a selecting portion, which, based on the dimension of the sheet material recognized by the recognizing portion, selects a sensor from the plurality of sensors, which requires the smallest amount of movement of the sheet material for positioning the sheet material at the predetermined position; and wherein the sheet material is detected by the selected sensor.
A sixteenth aspect of the present invention according to the fifteenth aspect is a sheet material positioning apparatus, wherein the corner of the sheet material is detected by the selected sensor.
A seventeenth aspect of the present invention according to the fifteenth aspect is a sheet material positioning apparatus further comprising a storing device, which stores the dimension of the sheet material recognized by the recognizing portion.